Protein kinases constitute a large family of structurally related enzymes that are responsible for the control of a variety of signal transduction processes within the cell. (See, Hardie, G. and Hanks, S. The Protein Kinase Facts Book, I and II, Academic Press, San Diego, Calif.: 1995). Protein kinases are attractive and proven targets for new therapeutic agents to treat a range if human diseases, with examples including Gleevec and Tarceva.
The Aurora kinases are especially attractive due to their association with numerous human cancers and the role they play in promoting proliferation of these cancer cells. (Harrington et al., Nature Med., 2004, 10, 262)
The Aurora proteins are a family of three highly related serine/threonine kinases (termed Aurora-A, -B and -C) that are essential for progression through the mitotic phase of cell cycle. Specifically Aurora-A plays a crucial role in centrosome maturation and segregation, formation of the mitotic spindle and faithful segregation of chromosomes. Aurora-B is a chromosomal passenger protein that plays a central role in regulating the alignment of chromosomes on the meta-phase plate, the spindle assembly checkpoint and for the correct completion of cytokinesis.
Overexpression of Aurora-A, -B or -C has been observed in a range of human cancers including colorectal, ovarian, gastric and invasive duct adenocarcinomas. In addition amplification of the AURKA locus that encodes for Aurora-A correlates with poor prognosis for patients with node-negative breast cancer. Furthermore overexpression of Aurora-A has been shown to transform mammalian fibroblasts, giving rise to aneuploid cells containing multipolar spindles.
A number of studies have now demonstrated that depletion or inhibition of Aurora-A or -B in human cancer cell lines by siRNA, dominant negative or neutralising antibodies disrupts progression through mitosis with accumulation of cells with 4N DNA, and in some cases this is followed by endoreduplication and cell death.